1. Field of the Invention
The present invention generally relates to a new and improved concrete road barrier having a low profile to achieve unprecedented visibility for drivers and outer sidewalls facing toward the road which angle outwardly from the barrier base so as to reduce the ramp and roll tendencies of vehicles impacting on the barrier.
2. Description of the Prior Art
Along most highways, there are hazards that present substantial danger to drivers of automobiles if they should happen to leave the highway. To help prevent such accidents, road barriers are often provided along the sides and in the median of a highway to channel the traffic onto appropriate lanes. These barriers are commonly made of concrete, and they slope gradually inwardly from the bottom to the top.
The use of road barriers has several important purposes. First, as noted above, the barriers are intended to channel vehicles hitting the barriers back into the adjacent traffic lanes. Second, the barriers are intended to help prevent vehicles from traveling entirely off the road or into the lanes of opposing traffic. Third, the barriers are intended to be stable and relatively immovable. It is also desirable that the barriers be easily assembled, and that they be weather resistant.
It is recognized that the physical size of many barriers is controlled to a great extent by norms of highway construction. Thus, most modern traffic lanes are designed to be about 12 feet wide. These dimensions, in turn, have caused portable concrete barriers to have a maximum width of about two feet; and they are generally composed of segments about 10 to 30 feet long. The barrier segments are commonly connected end-to-end by lengths of channel iron or angle iron fastened along the sides close to the lower surface of the barriers.
The mass of a barrier is important from the standpoint of resisting movement due to vehicle collisions and redirecting the colliding vehicles, when they strike the barrier. In general, barriers are most effective in handling passenger cars and vehicles of comparable size, especially when they impact the barriers at speeds of 60 mph and lower and at angles between the barrier's longitudinal axis and the vehicle's velocity vector less than about 25 degrees. Large trucks pose a much more difficult problem, since they are capable of simply smashing through barriers. In general, the mass of barriers becomes increasingly important with increasing vehicle size and speed.
The most commonly used barrier at the present time, the "CMB" (concrete median barrier) is a structural concrete barrier which is about two feet wide at its base and tapers inwardly to a height of 32 inches. The barrier at its top is typically about 6 inches wide. The inclined sidewalls of the barrier originally were purposely designed to enable a vehicle to ramp along and up the sidewalls so as to avoid metal damage to the vehicle. While the ramping ability has been considered to be a generally desirable feature, it may give rise to serious problems especially at high vehicle speeds. At these speeds, a vehicle has an increased tendency to climb a barrier and ultimately roll over.
Another problem with existing barriers lies in their height. The height of existing barriers, commonly about 32 inches, is often above or just below the eye level of persons in passenger vehicles -- i.e., about 30 to 36 inches above the road surface. Thus, barriers along a road may interfere with visibility of traffic and potential hazards or other obstacles. Blocking of vision by barriers lying between a highway and an access road or entrance ramp can be a particular problem, where the access road or ramp lies on a different plane than the highway.
A further problem with existing barriers involves the cost, attachment difficulties, and maintenance characteristic of current hardware used to join segments of concrete road barriers together.
Accordingly, a need persists for a more economic road barrier which can further reduce the risks of highway travel. Of particular interest are improved visibility and the restriction of vehicles to their proper traffic lanes with improved control and with reduced tendencies to scale barriers and to roll over.